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Wooden pavements
24~
Civil and MechanicalEngineering.
The grade of the approaches continues to descend until it strikes the surface of the ground. The superstructure will be placed below the grade of the road, except where it crosses the middle and Indiana chute. The lowest point of the superstructure over the middle chute, is 102} feet above low water, and over the Indiana chute, 96½ feet; the low water in the Indiana chute being six and a half'feet lower than in the middle chute. A draw-bridge of 114½ feet clear span on each side of the pivot pier, will be built over the canal. The entire length of the superstructure is 5,280 feet; the longest span is that over the middle chute, which is 370 feet. A peculiar feature consists in the fact that the railroad track is to be laid in the eentre, the two street tracks on either side ; one rail of the railroad track, in addition to another rail on either side, will form the two street railroad tracks. No street cars or other vehicles can cross at the same time as a locomotive, but street cars and common carriages can pass each other at any place on the bridge. The time occupied in crossing over the bridge by a locomotive and train, will be about five minutes. At present the Jeffersonville :Railroad runs daily, six trains each way over their road, and will, therefore, occupy the bridge for one hour in twenty.four. Of these, seven trains will cross over the bridge during the hours of 6 A . M . and 8 P. M., leaving, therefore, the use of the bridge for thirteen hours and twenty-five minutes unobstructed to the crossing of street cars and wagons. The superstructure of this bridge will consist of Fink's patent suspension trusses, except the channel spans, which are to be of the triangular plan, arranged by the same gentleman.
WOODEN PAVEMENTS, Reply and Report of CnAs. H. I{ASWELL,tO ~ communicationfrom a number of Tax-payer.~ of the City of New York. NEW YOR~:, Fel~ruary21st, 1868. Gg~l~I,E~Ex,--Your letter of the 13th inst., regarding Wooden ~treet Pavements, is received and considered, and in reply thereto, I submit as follows: The only wooden pavements now before the public for competi-
Wooden Pavements.
247
tion, that I have investigated, are those of Mr. Nicholson and Mr. C. Williams. That of Mr. Nicholson is constructed of white pine blocks three inches in width, six inches in depth, and of lengths varying from six to twelve inches, set transversely to the line of travel upon them, with an intervening space or fissure between their transverse courses, which is defined by a strip of wood laid at the base of the blocks; the wholeresting upon a layer of white pine boards over an ordinary sand-bed; and for the purpose of attaining durability of th~ wood, as alleged, its surface is coated but very imperfectly, with coal-tar. That of Mr. Williams is constructed of yellow pine blocks twelve inches square by six inches in depth, set directly in connection with each other, and resting upon a concrete of rubble and asphaltum, with g.rooves at proper intervals upon the face of the blocks, running transversely to the line of travel. The direct connection of one block with another, affords support to resist the lateral stress of travel, and the concrete gives support to the blocks in their resistance to a vertical stress. To meet the requirements of endurance to wear and resistance to decay, it is purposed to fill t h e pores of the wood with an oleaginous fluid, of such consistency as will retain its condition, and thereby not only preserve the wood from decay, but give such support to its fibres as will essentially add resistance to the crushing stress of loaded vehicles. This fluid is condensed from a vapor at high temperature, whereby the watery particles of the wood are dispelled, and the albumen solidified. Wood in its ordinary conditions, when used for pavements, is subjected to decay and the destruction of its fibres, by the crushing effbcts of loaded vehicles and horses. In the former case, if the wood is seasoned, it is subject to common rot, from its alternate exposure to moisture and dryness, and if it is unseasoned, it is subject to dry rot, by the putrefaction of its vegetable albumen and fermentable elements, as well as to the effect eonsequen.t upon its alternate exposure to moisture and dryness. Wood is altogether too porous in its structure, for endurance to the wear of loaded vehicles, and by the crushing of its fibres it is rendered liable to decay; for if it is seasoned, the abrasion of its surface and the imperfection of the coating, given it by Mr. Nieholson, exposes it to alterations of moisture and dryness, and if it is
248
Civil and Mechanical .EnFineering.
unseasoned, the coating of its surface with coal-tar or any like substance, by retaining the fluids, hasten its decay. There is a common but fallacious idea, that the charring of unseasoned timber, as is practised in setting fence posts, preserves it: on the contrary, the painting, coating or charring of unseasoned timber hastens its decay. Reviewing, then, the elements presented, I am of the opinion-1st. That wood in its ordinary condition, is unsuited as a material of pavement. 2d. That the wooden pavement now being laid in this city, will not meet the public demands in relation to its economy of maintenance and endurance to wear. 3d. That white pine or any other wood of lik e porous structure, is altogether unsuited for the requirements of a wooden pavement, unless its contained albumen has been solidified, its fluids expelled, and its pores filled with an antiseptic or oleaginous liquid of such consistency as will retain its condition. 4th. The immediate connection and consequent lateral support of one block with another, in the plan submitted by Mr. Williams, added to the great extent of the bottom surface, resting upon a bed of concrete, will ensure all the stability that it is practicable to give such a structure, within a practicable cost, and that the treatment for preservation as proposed by him, will ensure that endurance of the wood which the requirements of the case render imperative, in cost of maintenance, resistance to wear, and the sanitary condition of the city. Finally, so imperative are the requirements of durability even in woods exposed in a less manner than in street pavements, that talents and attainments of the highest order have been taxed to meet them, as developed in the essays of Ryan, Burnett, Boucheri, Bethel and Robbins. I am, respectfully, Yours, &c., CHAS. H. HASWELL.
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Civil and MechanicalEngineering.
The grade of the approaches continues to descend until it strikes the surface of the ground. The superstructure will be placed below the grade of the road, except where it crosses the middle and Indiana chute. The lowest point of the superstructure over the middle chute, is 102} feet above low water, and over the Indiana chute, 96½ feet; the low water in the Indiana chute being six and a half'feet lower than in the middle chute. A draw-bridge of 114½ feet clear span on each side of the pivot pier, will be built over the canal. The entire length of the superstructure is 5,280 feet; the longest span is that over the middle chute, which is 370 feet. A peculiar feature consists in the fact that the railroad track is to be laid in the eentre, the two street tracks on either side ; one rail of the railroad track, in addition to another rail on either side, will form the two street railroad tracks. No street cars or other vehicles can cross at the same time as a locomotive, but street cars and common carriages can pass each other at any place on the bridge. The time occupied in crossing over the bridge by a locomotive and train, will be about five minutes. At present the Jeffersonville :Railroad runs daily, six trains each way over their road, and will, therefore, occupy the bridge for one hour in twenty.four. Of these, seven trains will cross over the bridge during the hours of 6 A . M . and 8 P. M., leaving, therefore, the use of the bridge for thirteen hours and twenty-five minutes unobstructed to the crossing of street cars and wagons. The superstructure of this bridge will consist of Fink's patent suspension trusses, except the channel spans, which are to be of the triangular plan, arranged by the same gentleman.
WOODEN PAVEMENTS, Reply and Report of CnAs. H. I{ASWELL,tO ~ communicationfrom a number of Tax-payer.~ of the City of New York. NEW YOR~:, Fel~ruary21st, 1868. Gg~l~I,E~Ex,--Your letter of the 13th inst., regarding Wooden ~treet Pavements, is received and considered, and in reply thereto, I submit as follows: The only wooden pavements now before the public for competi-
Wooden Pavements.
247
tion, that I have investigated, are those of Mr. Nicholson and Mr. C. Williams. That of Mr. Nicholson is constructed of white pine blocks three inches in width, six inches in depth, and of lengths varying from six to twelve inches, set transversely to the line of travel upon them, with an intervening space or fissure between their transverse courses, which is defined by a strip of wood laid at the base of the blocks; the wholeresting upon a layer of white pine boards over an ordinary sand-bed; and for the purpose of attaining durability of th~ wood, as alleged, its surface is coated but very imperfectly, with coal-tar. That of Mr. Williams is constructed of yellow pine blocks twelve inches square by six inches in depth, set directly in connection with each other, and resting upon a concrete of rubble and asphaltum, with g.rooves at proper intervals upon the face of the blocks, running transversely to the line of travel. The direct connection of one block with another, affords support to resist the lateral stress of travel, and the concrete gives support to the blocks in their resistance to a vertical stress. To meet the requirements of endurance to wear and resistance to decay, it is purposed to fill t h e pores of the wood with an oleaginous fluid, of such consistency as will retain its condition, and thereby not only preserve the wood from decay, but give such support to its fibres as will essentially add resistance to the crushing stress of loaded vehicles. This fluid is condensed from a vapor at high temperature, whereby the watery particles of the wood are dispelled, and the albumen solidified. Wood in its ordinary conditions, when used for pavements, is subjected to decay and the destruction of its fibres, by the crushing effbcts of loaded vehicles and horses. In the former case, if the wood is seasoned, it is subject to common rot, from its alternate exposure to moisture and dryness, and if it is unseasoned, it is subject to dry rot, by the putrefaction of its vegetable albumen and fermentable elements, as well as to the effect eonsequen.t upon its alternate exposure to moisture and dryness. Wood is altogether too porous in its structure, for endurance to the wear of loaded vehicles, and by the crushing of its fibres it is rendered liable to decay; for if it is seasoned, the abrasion of its surface and the imperfection of the coating, given it by Mr. Nieholson, exposes it to alterations of moisture and dryness, and if it is
248
Civil and Mechanical .EnFineering.
unseasoned, the coating of its surface with coal-tar or any like substance, by retaining the fluids, hasten its decay. There is a common but fallacious idea, that the charring of unseasoned timber, as is practised in setting fence posts, preserves it: on the contrary, the painting, coating or charring of unseasoned timber hastens its decay. Reviewing, then, the elements presented, I am of the opinion-1st. That wood in its ordinary condition, is unsuited as a material of pavement. 2d. That the wooden pavement now being laid in this city, will not meet the public demands in relation to its economy of maintenance and endurance to wear. 3d. That white pine or any other wood of lik e porous structure, is altogether unsuited for the requirements of a wooden pavement, unless its contained albumen has been solidified, its fluids expelled, and its pores filled with an antiseptic or oleaginous liquid of such consistency as will retain its condition. 4th. The immediate connection and consequent lateral support of one block with another, in the plan submitted by Mr. Williams, added to the great extent of the bottom surface, resting upon a bed of concrete, will ensure all the stability that it is practicable to give such a structure, within a practicable cost, and that the treatment for preservation as proposed by him, will ensure that endurance of the wood which the requirements of the case render imperative, in cost of maintenance, resistance to wear, and the sanitary condition of the city. Finally, so imperative are the requirements of durability even in woods exposed in a less manner than in street pavements, that talents and attainments of the highest order have been taxed to meet them, as developed in the essays of Ryan, Burnett, Boucheri, Bethel and Robbins. I am, respectfully, Yours, &c., CHAS. H. HASWELL.
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